ASP.NET驗證碼

 
1.GSC_WebControlLibrary 這是在網上找到的一個控件，非常好用。但是效果不是特別好（見下圖。
）雖然容易使用，所有的屬性都可以像控件一樣設置，但是可用性不太高。用戶不能自定義，而且看起來這個驗證碼效果不太好。
效果：

2.用一個頁面生成圖片，另一個頁面調用，驗證碼存入cookie，調用時取cookie對比驗證.這個用戶就可以按自己的喜好更改效果和驗證碼的長度了 （：

效果如圖：

代碼如下：
CheckCode.aspx

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;

public partial class Tools_CheckCode : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        this.CreateCheckCodeImage(GenerateCheckCode());

    }

    private string GenerateCheckCode()
    {
        int number;
        char code;
        string checkCode = String.Empty;

        System.Random random = new Random();

        for (int i = 0; i < 5; i++)
        {
            number = random.Next();

            if (number % 2 == 0)
                code = (char)('0' + (char)(number % 10));
            else
                code = (char)('A' + (char)(number % 26));

            checkCode += code.ToString();
        }

        Response.Cookies.Add(new HttpCookie("CheckCode", checkCode));

        return checkCode;
    }

    private void CreateCheckCodeImage(string checkCode)
    {
        if (checkCode == null || checkCode.Trim() == String.Empty)
            return;

        System.Drawing.Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling((checkCode.Length * 12.5)), 22);
        Graphics g = Graphics.FromImage(image);

        try
        {
            //生成隨機生成器
            Random random = new Random();

            //清空圖片背景色
            g.Clear(Color.White);

            //畫圖片的背景噪音線
            for (int i = 0; i < 25; i++)
            {
                int x1 = random.Next(image.Width);
                int x2 = random.Next(image.Width);
                int y1 = random.Next(image.Height);
                int y2 = random.Next(image.Height);

                g.DrawLine(new Pen(Color.GreenYellow), x1, y1, x2, y2);
            }

            Font font = new System.Drawing.Font("Verdana", 12, (System.Drawing.FontStyle.Bold | System.Drawing.FontStyle.Italic));
            System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2f, true);
            g.DrawString(checkCode, font, brush, 2, 2);

            //畫圖片的前景噪音點
            for (int i = 0; i < 80; i++)
            {
                int x = random.Next(image.Width);
                int y = random.Next(image.Height);

                image.SetPixel(x, y, Color.FromArgb(random.Next()));
            }

            //畫圖片的邊框線
            g.DrawRectangle(new Pen(Color.Red), 0, 0, image.Width - 1, image.Height - 1);

            System.IO.MemoryStream ms = new System.IO.MemoryStream();
            image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
            Response.ClearContent();
            Response.ContentType = "image/Gif";
            Response.BinaryWrite(ms.ToArray());
        }
        finally
        {
            g.Dispose();
            image.Dispose();
        }
    }

}

然後在需要使用的頁面引用：
UseCheckCode.aspx
<img src="Tools/CheckCode.aspx" alt="驗證碼" style="width: 60px; height: 24px" />
3.用web handler生成圖片。這個其實和前面的意思大致差不多，調用方法也基本和2一樣,不同的是，他的驗證碼是存入Session的。供學習參考。

效果圖如下：

ValidateImageHandler.ashx
%@ WebHandler Language="C#" Class="ValidateImageHandler" %>

using System;
using System.Web;
using System.Web.SessionState;
using System.Drawing;
using System.Drawing.Imaging;
using System.Text;

/**//// <summary>
/// ValidateImageHandler 生成網站驗證碼功能
/// </summary>
public class ValidateImageHandler : IHttpHandler, IRequiresSessionState
{
    int intLength = 5;               //長度
    string strIdentify = "Identify"; //隨機字串存儲鍵值，以便存儲到Session中
    public ValidateImageHandler()
    {       
    }

    /**//// <summary>
    /// 生成驗證圖片核心代碼
    /// </summary>
    /// <param name="hc"></param>
    public void ProcessRequest(HttpContext hc)
    {
        //設置輸出流圖片格式
        hc.Response.ContentType = "image/gif";
       
        Bitmap b = new Bitmap(200, 60);
        Graphics g = Graphics.FromImage(b);
        g.FillRectangle(new SolidBrush(Color.YellowGreen), 0, 0, 200, 60);
        Font font = new Font(FontFamily.GenericSerif, 48, FontStyle.Bold, GraphicsUnit.Pixel);
        Random r = new Random();

        //合法隨機顯示字符列表
        string strLetters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890";
        StringBuilder s = new StringBuilder();
       
        //將隨機生成的字符串繪製到圖片上
        for (int i = 0; i < intLength; i++)
        {
            s.Append(strLetters.Substring(r.Next(0, strLetters.Length - 1), 1));
            g.DrawString(s[s.Length - 1].ToString(), font, new SolidBrush(Color.Blue), i * 38, r.Next(0, 15));
        }

        //生成干擾線條
        Pen pen = new Pen(new SolidBrush(Color.Blue), 2);
        for (int i = 0; i < 10; i++)
        {
            g.DrawLine(pen, new Point(r.Next(0, 199), r.Next(0, 59)), new Point(r.Next(0, 199), r.Next(0, 59)));
        }
        b.Save(hc.Response.OutputStream, ImageFormat.Gif);
        hc.Session[strIdentify] = s.ToString(); //先保存在Session中，驗證與用戶輸入是否一致
        hc.Response.End();
  
    }
   
    /**//// <summary>
    /// 表示此類實例是否可以被多個請求共用(重用可以提高性能)
    /// </summary>
    public bool IsReusable
    {
        get
        {
            return true;
        }
    }
}